The present invention relates generally to batteries, and more particularly relates to an air delivery system with a volume-changeable plenum for a metal-air battery.
Metal-air battery cells include an air permeable cathode and a metallic anode separated by an aqueous electrolyte. During discharge of a metal-air battery, such as a zinc-air battery, oxygen from the ambient air is converted at the cathode to hydroxide, zinc is oxidized at the anode by the hydroxide, and water and electrons are released to provide electrical energy. Metal-air batteries have a relatively high energy density because the cathode utilizes oxygen from ambient air as a reactant in the electrochemical reaction rather than a heavier material, such as a metal or metallic composition. Metal-air battery cells are often arranged in multiple cell packs within a common housing to provide a sufficient amount of power output. The result is a relatively light-weight battery.
To operate a metal-air battery cell, it is necessary therefore to provide a supply of oxygen to the air cathodes of the cells. An air pathway and a plenum are typically used to supply the air cathodes with the oxygen. The air pathway serves as a conduit of the oxygen and the plenum diffuses the oxygen evenly over the air cathodes so as to increase efficiency of the electrodes. The plenum, therefore, has to have a certain volume to work properly while the battery is operating. The air pathway is generally sealed or closed during non-use by sealing tapes, plugs, mechanical doors, etc., because water vapor and oxygen in the ambient air may cause the cell to flood, dry out, or discharge in certain circumstances, thereby leading to a reduction in cell efficiency and life. Furthermore, after a period of use, residual water vapor and oxygen in the plenum may cause similar problems, at least immediately after the air pathway is sealed or closed.
Thus, a need exists for an improved metal-air battery cell that overcomes or minimizes the above-referenced disadvantages of prior art metal-air battery cells.
The present invention satisfies the above-described needs by providing a novel metal-air battery. The metal-air battery of the present invention comprises one or more air cathodes; one or more air pathways from the air cathode to a reactive gas source; a closure member associated with each of the air pathways to selectively prevent the flow of gas through the air pathways; and one or more volume-changeable plenums in fluid communication with the air pathway and the air cathode.
The present invention also comprises a method of producing electricity using a metal-air battery comprising one or more air cathodes, an enclosure member at least partially defining a volume-changeable plenum in fluid communication with the air cathode, and at least one closable air pathway in fluid communication with the plenum and ambient air surrounding the enclosure. The method comprising the steps of opening the air pathway so that the ambient air can flow to said plenum through the pathway; and increasing the volume of the plenum so that air is drawn through the pathway to the plenum.
In another disclosed embodiment, the present invention comprises an electric device using the metal-air battery mentioned above.
Accordingly, it is an object of the present invention to provide an improved metal-air battery.
Another object of the present invention is to provide a metal-air battery that is relatively simple and inexpensive to manufacture.
A further object of the present invention is to provide a ventilation system for a metal-air battery that does not require any electric mechanisms to operate it.
Yet another object of the present invention is to provide a metal-air battery that reduces the amount of air in communication with the air cathode when the battery is not in use and increases the amount of air in communication with the air cathode when the battery is in use.
Another object of the present invention is to provide a metal-air battery with an initial charge of fresh reactive gas for reaction with an air cathode when the battery is activated.
These and other objects, features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments and the appended drawing and claims.